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Ecosystems and Communities The Role of Climate • If you live in Pennsylvania, you know you cannot grow banana trees in your backyard • Bananas are tropical plants that need plenty of water and heat • They won't survive in freezing temperatures • It may not be as obvious that cranberries won't grow in the Rio Grande Valley of Texas • Cranberries need plenty of water and a cold rest period • They cannot tolerate the months of very hot weather that often occur in the Rio Grande Valley The Role of Climate • Bananas and cranberries, like other plants and animals, vary in their adaptations to temperature, rainfall, and other environmental conditions • Species also vary in their tolerances for conditions outside their normal ranges • That's why climate is important in shaping ecosystems—and why understanding climate is important in ecology What Is Climate? • In the atmosphere, temperature, precipitation, and other environmental factors combine to produce weather and climate • Weather is the day-to-day condition of Earth's atmosphere at a particular time and place • The weather where you live may be clear and sunny one day but cloudy and cold the next • Climate, on the other hand, refers to the average, year-after-year conditions of temperature and precipitation in a particular region What Is Climate? • Climate is caused by the interplay of many factors, including the trapping of heat by the atmosphere, the latitude, the transport of heat by winds and ocean currents, and the amount of precipitation that results • The shape and elevation of landmasses also contribute to global climate patterns Water and Atmospheric Circulation • Top: Normal circulation • Bottom: El Nino years • Key: – Red arrows: movement of warm oceanic currents – Yellow arrows: movement of air What Is Climate? • The energy of incoming sunlight drives Earth's weather and helps determine climate • As you might expect, solar energy has an important effect on the temperature of the atmosphere • At the same time, the presence of certain gases in the atmosphere also has an effect on its temperature Greenhouse Effect • • • Temperatures on Earth remain within a range suitable for life because the biosphere has a natural insulating blanket—the atmosphere Carbon dioxide, methane, water vapor, and a few other atmospheric gases trap heat energy and maintain Earth's temperature range These gases function like the glass windows of a greenhouse – • Just as the glass keeps the greenhouse plants warm, these gases trap the heat energy of sunlight inside Earth's atmosphere The natural situation in which heat is retained by this layer of greenhouse gases is called the greenhouse effect, shown to the right Greenhouse Effect Greenhouse Effect • Carbon dioxide, water vapor, and several other gases in the atmosphere allow solar radiation to enter the biosphere but slow down the loss of heat to space • These greenhouse gases cause the greenhouse effect, which helps maintain Earth's temperature range Greenhouse Effect • • • • • Greenhouse gases allow solar energy to penetrate the atmosphere in the form of sunlight Much of the sunlight that hits the surface of our planet is converted into heat energy and then radiated back into the atmosphere However, those same gases do not allow heat energy to pass out of the atmosphere as readily as light energy enters it Instead, the gases trap heat inside Earth's atmosphere If these gases were not present in the atmosphere, Earth would be 30 degrees Celsius cooler than it is today Effect of Latitude on Climate • • • • • Because Earth is a sphere that is tilted on its axis, solar radiation strikes different parts of Earth's surface at an angle that varies throughout the year At the equator, the sun is almost directly overhead at noon all year At the North and South poles, however, the sun is much lower in the sky for months at a time Look at the figure below, and you will see that differences in the angle of sunlight directed at different latitudes result in the delivery of more heat to the equator than to the poles The difference in heat distribution with latitude has important effects on Earth's climate zones Effect of Latitude on Climate Climate Zones • Earth has three main climate zones • These climate zones are caused by the unequal heating of Earth's surface • Near the equator, energy from the sun strikes Earth almost directly • Near the poles, the sun's rays strike Earth's surface at a lower angle – The same amount of solar energy is spread out over a larger area, heating the surface less than at the equator Climate Zones • As a result of differences in latitude and thus the angle of heating, Earth has three main climate zones: – Polar zones are cold areas where the sun's rays strike Earth at a very low angle: • – Temperate zones sit between the polar zones and the tropics: • – These zones are located in the areas around the North and South poles, between 66.5° and 90° North and South latitudes Because temperate zones are more affected by the changing angle of the sun over the course of a year, the climate in these zones ranges from hot to cold, depending on the season Tropical zone, or tropics, is near the equator, between 23.5° North and 23.5° South latitudes: • The tropics thus receive direct or nearly direct sunlight year-round, making the climate almost always warm Heat Transport in the Biosphere • • • • • • The unequal heating of Earth's surface drives winds and ocean currents, which transport heat throughout the biosphere Winds form because warm air tends to rise and cool air tends to sink Consequently, air that is heated near the equator rises At the same time, cooler air over the poles sinks toward the ground The upward movement of warm air and the downward movement of cool air create air currents, or winds, that move heat throughout the atmosphere, from regions of sinking air to regions of rising air The prevailing winds, shown in the figure at right, bring warm or cold air to a region, affecting its climate Heat Transport in the Biosphere Heat Transport in the Biosphere • • • Similar patterns of heating and cooling occur in Earth's oceans Cold water near the poles sinks and then flows parallel to the ocean bottom, eventually rising again in warmer regions through a process called upwelling Meanwhile, surface water is moved by winds – In both cases, the water flow creates ocean currents • Like air currents, ocean currents transport heat energy within the biosphere: – Surface ocean currents warm or cool the air above them, thus affecting the weather and climate of nearby landmasses Heat Transport in the Biosphere Heat Transport in the Biosphere • Continents and other landmasses can also affect winds and ocean currents • Landmasses can interfere with the movement of air masses – Example: • A mountain range causes a moist air mass to rise • As this happens, the air mass cools and moisture condenses, forming clouds that bring precipitation to the mountains • Once the air mass reaches the far side of the mountains, it has lost much of its moisture • The result is a rain shadow—an area with a dry climate—on the far side of the mountains What Shapes an Ecosystem? • If you ask an ecologist where a particular organism lives, that person might say the organism lives on a Caribbean coral reef, or in an Amazon rain forest, or in a desert in the American Southwest – Those answers provide a kind of ecological address not unlike a street address in a city or town – An ecological address, however, tells you more than where an organism lives – It tells you about the climate the organism experiences and what neighbors it is likely to have • But what shapes the ecosystem in which an organism lives? Biotic and Abiotic Factors • Ecosystems are influenced by a combination of biological and physical factors • The biological influences on organisms within an ecosystem are called biotic factors – These include the entire living cast of characters with which an organism might interact, including birds, trees, mushrooms, and bacteria—in other words, the ecological community • Biotic factors that influence a bullfrog, for example, might include the tiny plants and algae it eats as a tadpole, the herons that eat the adult frog, and other species that compete with the bullfrog for food or space Biotic and Abiotic Factors • Physical, or nonliving, factors that shape ecosystems are called abiotic factors – Example: • The climate of an area includes abiotic factors such as temperature, precipitation, and humidity • Other abiotic factors are wind, nutrient availability, soil type, and sunlight • For example, an organism such as a bullfrog is affected by abiotic factors such as the availability of water and the temperature of the air • Together, biotic and abiotic factors determine the survival and growth of an organism and the productivity of the ecosystem in which the organism lives – The area where an organism lives is called its habitat – A habitat includes both biotic and abiotic factors Niche • If an organism's habitat is its address, its niche is its occupation • A niche is the full range of physical and biological conditions in which an organism lives and the way in which the organism uses those conditions – For instance, part of the description of an organism's niche includes its place in the food web – Another part of the description might include the range of temperatures that the organism needs to survive • The combination of biotic and abiotic factors in an ecosystem often determines the number of different niches in that ecosystem Niche • A niche includes the type of food the organism eats, how it obtains this food, and which other species use the organism as food – Example: • A mature bullfrog catches insects, worms, spiders, small fish, or even mice • Predators such as herons, raccoons, and snakes prey on bullfrogs Niche • The physical conditions that the bullfrog requires to survive are part of its niche • Bullfrogs spend their lives in or near the water of ponds, lakes, and slow-moving streams • A bullfrog's body temperature varies with that of the surrounding water and air • As winter approaches, bullfrogs burrow into the mud of pond or stream bottoms to hibernate Niche • The bullfrog's niche also includes when and how it reproduces • Female bullfrogs lay their eggs in water during the warmer months of the year • The young frogs, called tadpoles, live in the water until their legs and lungs develop Niche • As you will see, no two species can share the same niche in the same habitat • However, different species can occupy niches that are very similar • For instance, the three species of North American warblers shown in the figure at right live in the same spruce trees but feed at different elevations and in different parts of those trees • The species are similar, yet each warbler has a different niche within the forest Niche Community Interactions • When organisms live together in ecological communities, they interact constantly • These interactions help shape the ecosystem in which they live • Community interactions, such as competition, predation, and various forms of symbiosis, can powerfully affect an ecosystem Competition • Competition occurs when organisms of the same or different species attempt to use an ecological resource in the same place at the same time • The term resource refers to any necessity of life, such as water, nutrients, light, food, or space • In a forest, for example, broad-leaved trees such as oak or hickory may compete for sunlight by growing tall, spreading out their leaves, and blocking the sunlight from shorter trees • Similarly, two species of lizards in a desert might compete by attempting to eat the same type of insect Competition • • • • Direct competition in nature often results in a winner and a loser—with the losing organism failing to survive A fundamental rule in ecology, the competitive exclusion principle, states that no two species can occupy the same niche in the same habitat at the same time Look again at the distribution of the warblers in the figure at right Can you see how this distribution avoids direct competition among the different warbler species? INTERSPECIFIC COMPETITION COMPETITIVE EXCLUSION PRINCIPLE • These species of warblers have adapted so that each species eats primarily at a different level of the tree • This adaptation has reduced the interspecific competition among them Predation • An interaction in which one organism captures and feeds on another organism is called predation • The organism that does the killing and eating is called the predator, and the food organism is the prey • Cheetahs are active predators with claws and sharp teeth: – Their powerful legs enable them to run after prey • Other predators, such as anglerfishes, are more passive: – An anglerfish has a fleshy appendage that resembles a fishing lure, which it uses to draw unsuspecting prey close to its mouth Predator-Prey Relationship Predator-Prey Relationship • Each animal controls the other animal’s cycle • Cycles fluctuate together Symbiosis • Any relationship in which two species live closely together is called symbiosis, which means living together • Biologists recognize three main classes of symbiotic relationships in nature: – Mutualism – Commensalism – Parasitism Symbiosis • Symbiosis: Biological relationship in which two dissimilar organisms live together in a close relationship – Three main types: • Mutualism: both organisms benefit from living together – Intestinal bacteria and cattle – Algae and clam – Ants and aphids • Commensalism: one organism benefits and the other neither benefits nor suffers harm – Epiphytes – Shrimp and sea cucumber – Orchid and perch tree • Parasitism: close, long-term relationship – One organism (parasite) obtains its nutrition from another organism (host) » Mistletoe in a mesquite tree » Tick Mutualism • In mutualism, both species benefit from the relationship • Many flowers, for example, depend on certain species of insects to pollinate them • The flowers provide the insects with food in the form of nectar, pollen, or other substances, and the insects help the flowers reproduce Mutualism • Mutualism: both organisms benefit from living together – Intestinal bacteria and cattle – Algae and clam – Ants and aphids: • The ant cares for the aphids and protects them from predators • The aphids produce a sweet liquid that the ant drinks Mutualism MUTUALISM • A clam and algae Commensalism • In commensalism, one member of the association benefits and the other is neither helped nor harmed • Small marine animals called barnacles, for example, often attach themselves to a whale's skin – The barnacles perform no known service to the whale, nor do they harm it – Yet, the barnacles benefit from the constant movement of water past the swimming whale, because the water carries food particles to them Commensalism • Commensalism: one organism benefits and the other neither benefits nor suffers harm – Epiphytes – Shrimp and sea cucumber – Orchid and perch tree • The orchid benefits from its perch in the tree as it absorbs water and minerals from rainwater and runoff, but the tree is not affected Commensalism COMMENSALISM • A shrimp and sea cucumber Parasitism • In parasitism, one organism lives on or inside another organism and harms it • The parasite obtains all or part of its nutritional needs from the other organism, called the host • Generally, parasites weaken but do not kill their host, which is usually larger than the parasite • Tapeworms, for example, are parasites that live in the intestines of mammals • Fleas, ticks, and lice live on the bodies of mammals, feeding on the blood and skin of the host Parasitism • Parasitism: close, long-term relationship – One organism (parasite) obtains its nutrition from another organism (host) • Mistletoe in a mesquite tree • Tick: – A tick feeds on the blood of its host and may also carry disease-causing microorganisms Parasitism PARASITISM • Mistletoe in a mesquite tree Ecological Succession • On the time scale of a human life, some ecosystems may seem stable • The appearance of stability is often misleading, because ecosystems and communities are always changing • Sometimes, an ecosystem changes in response to an abrupt disturbance, such as a severe storm • At other times, change occurs as a more gradual response to natural fluctuations in the environment Ecological Succession • Ecosystems are constantly changing in response to natural and human disturbances • As an ecosystem changes, older inhabitants gradually die out and new organisms move in, causing further changes in the community • This series of predictable changes that occurs in a community over time is called ecological succession • Sometimes succession results from slow changes in the physical environment • A sudden natural disturbance from human activities, such as clearing a forest, may also be a cause of succession Primary Succession • On land, succession that occurs on surfaces where no soil exists is called primary succession – Example: • Occurs on the surfaces formed as volcanic eruptions build new islands or cover the land with lava rock or volcanic ash • Primary succession also occurs on bare rock exposed when glaciers melt. SUCCESSION • Orderly change in the inhabitants of an area • Gradual, sequential replacement of populations in an area: – Each intermediate community is called a Seral Community – Final community that remains stable as long as the area is undisturbed is the Climax Community Primary Succession • • • • • • • In the figure below, you can follow the stages of primary succession after a volcanic eruption When primary succession begins, there is no soil, just ash and rock The first species to populate the area are called pioneer species The pioneer species on volcanic rocks are often lichens A lichen is made up of a fungus and an alga and can grow on bare rock As lichens grow, they help break up the rocks When they die, the lichens add organic material to help form soil in which plants can grow Primary Succession Lake is gradually being filled by vegetation PRIMARY SUCCESSION • Sequential replacement of populations in an area that has not previously supported life – Bare rock, sand dune, volcanic island • Pond becomes shallow over time because of sediments, volcano forms island, or asphalted parking lot – New barren soil formed • First plants (pioneer species) to establish create a pioneer community • Gradual changes create a climax community Secondary Succession • Components of an ecosystem can be changed by natural events, such as fires, or by human activities, such as farming • These changes may affect the ecosystem in predictable or unpredictable ways • When the disturbance is over, community interactions tend to restore the ecosystem to its original condition through secondary succession – Example: • Secondary succession occurs after wildfires burn woodlands and when land cleared for farming is abandoned • In fact, fires set by lightning occur in many ecosystems, and some plants are so adapted to periodic fires that their seeds won't sprout unless exposed to fire! Secondary Succession • Ecologists used to think that succession in a given area always proceeded through predictable stages to produce the same stable climax community • Old-growth forests in the Pacific Northwest, for example, were considered climax communities • But natural disasters, climate change, and human activity such as introduction of nonnative species profoundly affect these communities today • Healthy ecosystems usually recover from natural disturbances because of the way components of the system interact • Ecosystems may or may not recover from long-term, human-caused disturbances SECONDARY SUCCESSION • Sequential replacement of populations in disrupted habitats that have been not been totally stripped of soil and vegetation • Climax community destroyed – Fire, farmer clears field • Eventually reaches a climax community SUCCESSION IN LAKES • • • • • • Oligotrophic Lake Eutrophic Lake Marsh Swamp Dry land Dense Forest Succession in a Marine Ecosystem • • • • • • Succession can occur in any ecosystem—even in the permanently dark, deep ocean In 1987, scientists found an unusual community of organisms living on the remains of a dead whale in the deep waters off the coast of southern California At first, ecologists did not know what to make of this extraordinary community After several experiments and hours of observation, the ecologists found that the community represented a stage in succession amid an otherwise stable and well-documented deep-sea ecosystem Since that discovery, several more whale carcasses have been found in other ocean basins with similar organisms surrounding them The figure below illustrates three stages in the succession of a whale-fall community Succession in a Marine Ecosystem Succession in a Marine Ecosystem • • The disturbance that causes this kind of succession begins when a large whale, such as a blue or fin whale, dies and sinks to the normally barren ocean floor The whale carcass attracts a host of scavengers and decomposers, including amphipods, hagfishes, and sharks, that feast on the decaying meat Succession in a Marine Ecosystem • Within a year, most of the whale's tissues have been eaten • The carcass then supports only a much smaller number of fishes, crabs, marine snails, and other marine animals • The decomposition of the whale's body, however, enriches the surrounding sediments with nutrients, forming an oasis of sediment dwellers, including many different species of marine worms Succession in a Marine Ecosystem • • • • When only the whale's skeleton remains, a third community moves in Heterotrophic bacteria begin to decompose oils inside the whale bones In doing so, they release chemical compounds that serve as energy sources for other bacteria that are chemosynthetic autotrophs The chemosynthetic bacteria, in turn, support a diverse community of mussels, limpets, snails, worms, crabs, clams, and other organisms that live on the bones and within the nearby sediments Biomes • Ecologists group Earth's diverse environments into biomes • A biome is a complex of terrestrial communities that covers a large area and is characterized by certain soil and climate conditions and particular assemblages of plants and animals Biomes • Can all kinds of organisms live in every biome? No • Species vary in their adaptations to different conditions • An adaptation is an inherited characteristic that increases an organism's ability to survive and reproduce Biomes • The leaves of the saguaro cactus, for example, are reduced to spines to minimize water loss, and its stems store water during dry spells – Its shallow, wide-spreading roots absorb water rapidly • Desert rodents, such as kangaroo rats, have adaptations in their kidneys that help conserve water, and they extract water from food • Many rain forest plants, such as certain anthuriums, have long, thin leaves whose pointed tips help shed excess water • Some rain forest animals, such as certain tree frogs, spend their life in trees—their tadpoles grow in water pockets in leaf bases of plants such as bromeliads Biomes • These sorts of variations in plants and animals help different species survive under different conditions in different biomes • Plants and animals also exhibit variations in tolerance, or ability to survive and reproduce under conditions that differ from their optimal conditions – Plants and animals of the Arizona desert, for example, can tolerate temperatures that range from blisteringly hot to below freezing – Some rain forest plants and animals, by comparison, die quickly if the temperature drops below freezing or rises above 34°C for long • Either too much or too little of any environmental factor can make it difficult for an organism to survive – A saguaro would rot and die in a rain forest as surely as an anthurium or rain forest tree frog would shrivel and die in the desert! Biomes and Climate • • • Because each species is adapted to certain conditions, the climate of a region is an important factor in determining which organisms can survive there Even within a biome, precise conditions of temperature and precipitation can vary over small distances The climate in a small area that differs from the climate around it is called a microclimate – Example: • • Certain streets in San Francisco are often blanketed in fog while the sun shines brightly just a few blocks away Two main components of climate—temperature and precipitation—can be summarized in a graph called a climate diagram, as shown in the figure below Biomes and Climate A Climate Diagram • Climate diagrams show the average temperature and precipitation at a given location during each month of the year • In this graph, and the others to follow, temperature is plotted as a red line • Precipitation is shown as vertical purple bars Major Biomes • Ecologists recognize at least ten different biomes • The world's major biomes include tropical rain forest, tropical dry forest, tropical savanna, desert, temperate grassland, temperate woodland and shrubland, temperate forest, northwestern coniferous forest, boreal forest, and tundra • Each of these biomes is defined by a unique set of abiotic factors—particularly climate—and a characteristic assemblage of plants and animals • The distribution of major biomes is shown in the figure at right, and some of their most important characteristics are summarized in the next 10 screens Major Biomes TERRESTRIAL BIOMES • Biome: large area identified by the presence of characteristic plants and animals – Identified by their dominant plant – Each has its own characteristic types of plants and animals Major Biomes • There is often ecological variation within a biome • Sometimes, this variation is due to changes in microclimate caused by differences in exposure or elevation above sea level • Other times, variation may be related to local soil conditions or the presence of rock outcroppings • Note also that although boundaries between biomes on this map appear to be sharp, there are often transitional areas in which one biome's plants and animals become less common, whereas organisms of the adjacent biome become more common • These variations in distribution often can be related to the ranges of tolerances of plants and animals for different environmental factors • As you look at the figure Major Biomes and the following photographs and climate diagrams, see if you can relate the characteristics and locations of biomes to the patterns of global winds and ocean currents in the figure Heat Transport Tropical Rain Forest • Tropical rain forests are home to more species than all other biomes combined • The leafy tops of tall trees—extending from 50 to 80 meters above the forest floor—form a dense covering called a canopy • In the shade below the canopy, a second layer of shorter trees and vines forms an understory • Organic matter that falls to the forest floor quickly decomposes, and the nutrients are recycled: nutrient poor soil Tropical Rain Forest • • • • Abiotic factors: hot and wet yearround; thin, nutrient-poor soils Dominant plants: broad-leaved evergreen trees; ferns; large woody vines and climbing plants; orchids and bromeliads Dominant wildlife: herbivores such as sloths, tapirs, and capybaras; predators such as jaguars; anteaters; monkeys; birds such as toucans, parrots, and parakeets; insects such as butterflies, ants, and beetles; piranhas and other freshwater fishes; reptiles such as caymans, boa constrictors, and anacondas Geographic distribution: parts of South and Central America, Southeast Asia, parts of Africa, southern India, and northeastern Australia Tropical Rain Forest Tropical Dry Forest • Tropical dry forests grow in places where rainfall is highly seasonal rather than year-round • During the dry season, nearly all the trees drop their leaves to conserve water • A tree that sheds its leaves during a particular season each year is called deciduous Tropical Dry Forest • • • • Abiotic factors: generally warm yearround; alternating wet and dry seasons; rich soils subject to erosion Dominant plants: tall, deciduous trees that form a dense canopy during the wet season; drought-tolerant orchids and bromeliads; aloes and other succulents Dominant wildlife: tigers; monkeys; herbivores such as elephants, Indian rhinoceroses, hog deer; birds such as great pied hornbills, pied harriers, and spot-billed pelicans; insects such as termites; reptiles such as snakes and monitor lizards Geographic distribution: parts of Africa, South and Central America, Mexico, India, Australia, and tropical islands Tropical Dry Forest Tropical Savanna • Receiving more seasonal rainfall than deserts but less than tropical dry forests, tropical savannas, or grasslands, are characterized by a cover of grasses • Savannas are spotted with isolated trees and small groves of trees and shrubs • Compact soils, fairly frequent fires, and the action of large animals such as rhinoceroses prevent some savanna areas from turning into dry forest Tropical Savanna • • • • Abiotic factors: warm temperatures; seasonal rainfall; compact soil; frequent fires set by lightning Dominant plants: tall, perennial grasses; sometimes drought-tolerant and fire-resistant trees or shrubs Dominant wildlife: predators such as lions, leopards, cheetahs, hyenas, and jackals; aardvarks; herbivores such as elephants, giraffes, antelopes, and zebras; baboons; birds such as eagles, ostriches, weaver birds, and storks; insects such as termites Geographic distribution: large parts of eastern Africa, southern Brazil, and northern Australia Tropical Savanna Desert • All deserts are dry — in fact, a desert biome is defined as having annual precipitation of less than 25 centimeters – Beyond that, deserts vary greatly, depending on elevation and latitude • Many undergo extreme temperature changes during the course of a day, alternating between hot and cold • The organisms in this biome can tolerate the extreme conditions Desert • • • • Abiotic factors: low precipitation; variable temperatures; soils rich in minerals but poor in organic material Dominant plants: cacti and other succulents; creosote bush and other plants with short growth cycles Dominant wildlife: predators such as mountain lions, gray foxes, and bobcats; herbivores such as mule deer, pronghorn antelopes, desert bighorn sheep, and kangaroo rats; bats; birds such as owls, hawks, and roadrunners; insects such as ants, beetles, butterflies, flies, and wasps; reptiles such as tortoises, rattlesnakes, and lizards Geographic distribution: Africa, Asia, the Middle East, United States, Mexico, South America, and Australia Desert Temperate Grassland • Characterized by a rich mix of grasses and underlaid by some of the world's most fertile soils, temperate grasslands—such as plains and prairies—once covered vast areas of the midwestern and central United States • Since the development of the steel plow, however, most have been converted to agricultural fields • Periodic fires and heavy grazing by large herbivores maintain the characteristic plant community Temperate Grassland • • • • Abiotic factors: warm to hot summers; cold winters; moderate, seasonal precipitation; fertile soils; occasional fires Dominant plants: lush, perennial grasses and herbs; most are resistant to drought, fire, and cold Dominant wildlife: predators such as coyotes and badgers—historically included wolves and grizzly bears; herbivores such as mule deer, pronghorn antelopes, rabbits, prairie dogs, and introduced cattle— historically included bison; birds such as hawks, owls, bobwhites, prairie chickens, mountain plovers; reptiles such as snakes; insects such as ants and grasshoppers Geographic distribution: central Asia, North America, Australia, central Europe, and upland plateaus of South America Temperate Grassland Temperate Woodland and Shrubland • This biome is characterized by a semiarid climate and a mix of shrub communities and open woodlands • In the open woodlands, large areas of grasses and wildflowers such as poppies are interspersed with oak trees • Communities that are dominated by shrubs are also known as chaparral • The growth of dense, low plants that contain flammable oils makes fires a constant threat Temperate Woodland and Shrubland • • • • Abiotic factors: hot, dry summers; cool, moist winters; thin, nutrient-poor soils; periodic fires Dominant plants: woody evergreen shrubs with small, leathery leaves; fragrant, oily herbs that grow during winter and die in summer Dominant wildlife: predators such as coyotes, foxes, bobcats, and mountain lions; herbivores such as blacktailed deer, rabbits, and squirrels; birds such as hawks, California quails, warblers and other songbirds; reptiles such as lizards and snakes; butterflies Geographic distribution: western coasts of North and South America, areas around the Mediterranean Sea, South Africa, and Australia Temperate Woodland and Shrubland Temperate Forest • Temperate forests contain a mixture of deciduous and coniferous trees • Coniferous trees, or conifers, produce seed-bearing cones and most have leaves shaped like needles – These forests have cold winters that halt plant growth for several months • In autumn, the deciduous trees shed their leaves • In the spring, small plants burst out of the ground and flower. • Soils of temperate forests are often rich in humus, a material formed from decaying leaves and other organic matter that makes soil fertile Temperate Forest • • • • Abiotic factors: cold to moderate winters; warm summers; yearround precipitation; fertile soils Dominant plants: broadleaf deciduous trees; some conifers; flowering shrubs; herbs; a ground layer of mosses and ferns Dominant wildlife: Deer; black bears; bobcats; nut and acorn feeders such as squirrels; omnivores such as raccoons and skunks; numerous songbirds; turkeys Geographic distribution: eastern United States; southeastern Canada; most of Europe; and parts of Japan, China, and Australia Temperate Forest Northwestern Coniferous Forest • Mild, moist air from the Pacific Ocean provides abundant rainfall to this biome • The forest is made up of a variety of conifers, ranging from giant redwoods along the coast of northern California to spruce, fir, and hemlock farther north • Moss often covers tree trunks and the forest floor • Flowering trees and shrubs such as dogwood and rhododendron are also abundant • Because of its lush vegetation, the northwestern coniferous forest is sometimes called a temperate rain forest Northwestern Coniferous Forest • • • • Abiotic factors: mild temperatures; abundant precipitation during fall, winter, and spring; relatively cool, dry summer; rocky, acidic soils Dominant plants: Douglas fir, Sitka spruce, western hemlock, redwood Dominant wildlife: bears; large herbivores such as elk and deer; beavers; predators such as owls, bobcats, and members of the weasel family Geographic distribution: Pacific coast of northwestern United States and Canada, from northern California to Alaska Northwestern Coniferous Forest Boreal Forest • Along the northern edge of the temperate zone are dense evergreen forests of coniferous trees • These biomes are called boreal forests, or taiga • Winters are bitterly cold, but summers are mild and long enough to allow the ground to thaw • The word boreal comes from the Greek word for “north,” reflecting the fact that boreal forests occur mostly in the Northern Hemisphere Boreal Forest • • • • Abiotic factors: long, cold winters; short, mild summers; moderate precipitation; high humidity; acidic, nutrient-poor soils Dominant plants: needleleaf coniferous trees such as spruce and fir; some broadleaf deciduous trees; small, berry-bearing shrubs Dominant wildlife: predators such as lynxes and timber wolves and members of the weasel family; small herbivorous mammals; moose and other large herbivores; beavers; songbirds and migratory birds Geographic distribution: North America, Asia, and northern Europe Boreal Forest Tundra • The tundra is characterized by permafrost, a layer of permanently frozen subsoil • During the short, cool summer, the ground thaws to a depth of a few centimeters and becomes soggy and wet • In winter, the topsoil freezes again • This cycle of thawing and freezing, which rips and crushes plant roots, is one reason that tundra plants are small and stunted • Cold temperatures, high winds, the short growing season, and humus-poor soils also limit plant height Tundra • • • • Abiotic factors: strong winds; low precipitation; short and soggy summers; long, cold, and dark winters; poorly developed soils; permafrost Dominant plants: groundhugging plants such as mosses, lichens, sedges, and short grasses Dominant wildlife: a few resident birds and mammals that can withstand the harsh conditions; migratory waterfowl, shore birds, musk ox, Arctic foxes, and caribou; lemmings and other small rodents Geographic distribution: northern North America, Asia, and Europe Tundra Other Land Areas • Some areas of land on Earth do not fall neatly into the major biome categories • These areas include mountain ranges and polar ice caps Mountain Ranges • Mountain ranges can be found on all continents • On mountains such as Washington's Mount Rainier, the abiotic and biotic conditions vary with elevation • As you move up from base to summit, temperatures become colder and precipitation increases • Therefore, the types of plants and animals also change • If you were to climb the Rocky Mountains in Colorado, for example, you would begin in a grassland • Then, you would pass through an open woodland of pines • Next, you would hike through a forest of spruce and other conifers • Near the summit, you would reach open areas of wildflowers and stunted vegetation resembling tundra • In the Canadian Rockies, ice fields occur at the peaks of some ranges LIFE ZONES IN MOUNTAINS POLAR BIOMES • Earth’s coldest regions – Covered in ice • • • • • North/South Pole Tops of mountains Moss, lichens Almost no precipitation Scarce freshwater Polar Ice Caps • The icy polar regions that border the tundra are cold year-round • Outside of the ice and snow, plants and algae are few but do include mosses and lichens • In the north polar region, the Arctic Ocean is covered with sea ice, and a thick ice cap covers most of Greenland – Polar bears, seals, insects, and mites are the dominant animals • In the south polar region, the continent of Antarctica is covered by a layer of ice that is nearly 5 kilometers thick in some places – There, the dominant wildlife includes penguins and marine mammals Aquatic Ecosystems • Nearly three fourths of Earth's surface is covered with water, so it is not surprising that many organisms make their homes in aquatic habitats • Oceans, streams, lakes, and marshes: – Indeed, nearly any body of water contains a wide variety of communities • These aquatic communities are governed by biotic and abiotic factors, including light, nutrient availability, and oxygen AQUATIC BIOMES • Occupy the majority of the surface of the earth • Characterized by salt concentration Aquatic Ecosystems • Aquatic ecosystems are determined primarily by the depth, flow, temperature, and chemistry of the overlying water – In contrast to land biomes, which are grouped geographically, aquatic ecosystems are often grouped according to the abiotic factors that affect them • One such factor is the depth of water, or distance from shore – The depth of water, in turn, determines the amount of light that organisms receive Aquatic Ecosystems • Water chemistry refers primarily to the amount of dissolved chemicals—especially salts, nutrients, and oxygen—on which life depends – Example: • Communities of organisms found in shallow water close to shore can be very different from the communities that occur away from shore in deep water • One abiotic factor that is important both to biomes and aquatic ecosystems is latitude • Aquatic ecosystems in polar, temperate, and tropical oceans all have distinctive characteristics Freshwater Ecosystems • It may surprise you to know that only 3 percent of the surface water on Earth is fresh water • Freshwater ecosystems can be divided into two main types: – Flowing-water ecosystems – Standing-water ecosystems FRESHWATER BIOME • Salt concentration about 0.005% Flowing-Water Ecosystems • Rivers, streams, creeks, and brooks are all freshwater ecosystems that flow over the land • Organisms that live there are well adapted to the rate of flow • Some insect larvae have hooks that allow them to take hold of aquatic plants • Certain catfish have suckers that anchor them to rocks • Trout and many other fishes have streamlined bodies that help them move with or against the current Flowing-Water Ecosystems • Flowing-water ecosystems, such as rivers, originate in mountains or hills, often springing from an underground water source • Near the source, the turbulent water has plenty of dissolved oxygen but little plant life • As the water flows downhill, sediments build up and enable plants to establish themselves • Farther downstream, the water may meander more slowly through flat areas, where turtles, beavers, or river otters make their homes RIVERS AND STREAMS • River: body of water that flows from the headwaters down a gradient (slope) towards its mouth – Steep gradient: • Fast current – Low gradient: • Slow current Standing-Water Ecosystems • Lakes and ponds are the most common standing-water ecosystems • In addition to the net flow of water in and out of these systems, there is usually water circulating within them – This circulation helps to distribute heat, oxygen, and nutrients throughout the ecosystem Standing-Water Ecosystems • The relatively still waters of lakes and ponds provide habitats for many organisms, such as plankton, that would be quickly washed away in flowing water • Plankton is a general term for the tiny, free-floating organisms that live in both freshwater and saltwater environments • Unicellular algae, or phytoplankton, are supported by nutrients in the water and form the base of many aquatic food webs • Planktonic animals, or zooplankton, feed on the phytoplankton LAKES AND PONDS • Two categories: – Eutrophic: • Rich in organic matter and vegetation • Murky water – Oligotrophic: • Little organic matter • Clear water Freshwater Wetlands • A wetland is an ecosystem in which water either covers the soil or is present at or near the surface of the soil for at least part of the year • The water in wetlands may be flowing or standing and fresh, salty, or brackish, which is a mixture of fresh and salt water • Many wetlands are very productive ecosystems that serve as breeding grounds for insects, fishes and other aquatic animals, amphibians, and migratory birds Freshwater Wetlands • The three main types of freshwater wetlands are: – Bogs – Marshes – Swamps Freshwater Wetlands • Bogs: – Wetlands that are often dominated by sphagnum moss, typically form in depressions where water collects – The water in sphagnum bogs is often very acidic Freshwater Wetlands • Marshes: – Shallow wetlands along rivers – They may be underwater for all or part of the year – Marshes often contain cattails, rushes, and other tall, grasslike plants Freshwater Wetlands • Swamps: – Water flows slowly through swamps, which often look like flooded forests – The presence of trees and shrubs is what distinguishes a swamp from a marsh – Some wetlands, such as swamps, are wet year-round – Example: • Swamp along the Loxahatchee River in Florida is home to turtles, otters, alligators, and herons that live among the bald cypress trees Freshwater Wetlands • Other kinds of wetlands, however, may not always be covered in standing water • Such areas may be classified as wetlands because they have certain kinds of soils and are wet enough to support a specific community of water-loving plants and animals Estuaries • Wetlands formed where rivers meet the sea • Estuaries thus contain a mixture of fresh water and salt water, and are affected by the rise and fall of ocean tides • Many are shallow, so sufficient sunlight reaches the bottom to power photosynthesis • Primary producers include plants, algae, and both photosynthetic and chemosynthetic bacteria • Estuary food webs differ from those of more familiar ecosystems because most primary production is not consumed by herbivores – Instead, much of that organic material enters the food web as detritus • Detritus is made up of tiny pieces of organic material that provide food for organisms at the base of the estuary's food web – Organisms that feed on detritus include clams, worms, and sponges ESTUARY • River freshwater and ocean saltwater mix • Periodic variation in temperature and salinity because of tides Estuaries • Estuaries support an astonishing amount of biomass, although they usually contain fewer species than freshwater or marine ecosystems • Estuaries serve as spawning and nursery grounds for commercially important fishes and for shellfish such as shrimps and crabs – Many young animals feed and grow in estuaries, then head out to sea to mature, and return to reproduce • Many waterfowl use estuaries for nesting, feeding, and resting during migrations Estuaries Salt Marshes • Temperate-zone estuaries dominated by salttolerant grasses above the low-tide line, and by seagrasses under water • Salt marshes occur in estuaries along seacoasts in the temperate zone • They are (or were once) found along great stretches of eastern North America from southern Maine to Georgia • One of the largest systems of connected salt marshes in America surrounds the Chesapeake Bay estuary in Maryland Estuaries Mangrove Swamps • Coastal wetlands that occur in bays and estuaries across tropical regions, including southern Florida and Hawaii • Here, the dominant plants are several species of salt-tolerant trees, collectively called mangroves • Seagrasses are also common below the low-tide line • Like salt marshes, mangrove swamps are valuable nurseries for fishes and shellfishes • The largest mangrove area in the continental United States is within Florida's Everglades National Park MARINE BIOME • Three areas: – Ocean – Intertidal (Littoral Zone) – Estuary Marine Ecosystems • Unless you are an avid diver or snorkeler, it takes some imagination to picture what life is like in the vast, threedimensional ocean • Sunlight penetrates only a relatively short distance through the surface of the water • Photosynthesis is limited to this well-lit upper layer known as the photic zone – Only in this relatively thin surface layer—typically down to a depth of about 200 meters—can algae and other producers grow • Below the photic zone is the aphotic zone, which is permanently dark – Chemosynthetic autotrophs are the only producers that can survive in the aphotic zone Marine Ecosystems • There are several different classification systems that scientists use to describe marine ecosystems • In addition to the division between the photic and aphotic zones, marine biologists divide the ocean into zones based on the depth and distance from shore: – Intertidal zone – Coastal ocean – Open ocean • Each of these zones supports distinct ecological communities • The benthic zone covers the ocean floor and is, therefore, not exclusive to any of the other marine zones • The figure at right shows a generalized diagram of the marine zones Marine Ecosystems OCEAN • • • 70% of the earth Salt concentration about 3.5% – Mostly NaCl Two zones: – Pelagic (open ocean) • Vertically: – Photic; light penetrates (photosynthesis) – Aphotic: no light penetrates • Horizontally: – Neritic: continental shelf (Sublittoral Zone) (abundant life) – Oceanic: deep water of open ocean – Benthic (Abyssal Zone) (ocean bottom) INTERTIDAL • Organisms adapted to periodic dryness and submersion Intertidal Zone • Organisms that live in the intertidal zone are exposed to regular and extreme changes in their surroundings • Once or twice a day, they are submerged in sea water • The remainder of the time, they are exposed to air, sunlight, and temperature changes • Often, organisms in this zone are battered by waves and sometimes by strong currents Intertidal Zone • There are many different types of intertidal communities • One of the most interesting is the rocky intertidal, which exists in temperate regions where exposed rocks line the shore • There, barnacles and seaweed permanently attach themselves to the rocks • Other organisms, such as snails, sea urchins, and sea stars, cling to the rocks by their feet or suckers Intertidal Zone • Competition among organisms in the rocky intertidal zone often leads to zonation • Zonation is the prominent horizontal banding of organisms that live in a particular habitat • In the rocky intertidal zone, each band can be distinguished by differences in color or shape of the major organisms – For example, a band of black algae might grow at the highest high-tide line, followed by encrusting barnacles • Lower down, clusters of blue mussels might stick out amid clumps of green algae • This zonation is similar to the pattern that you might observe as you climb up a mountain • In the intertidal zone, however, zonation exists on a smaller vertical scale—just a few meters compared to the kilometers you would ascend on a mountain Coastal Ocean • The coastal ocean extends from the low-tide mark to the outer edge of the continental shelf, the relatively shallow border that surrounds the continents • The continental shelf is often shallow enough to fall mostly or entirely within the photic zone, so photosynthesis can usually occur throughout its depth • As a result, the coastal ocean is often rich in plankton and many other organisms Coral Reefs • In the warm, shallow water of tropical coastal oceans are coral reefs, among the most diverse and productive environments on Earth • Coral reefs are named for the coral animals whose hard, calcium carbonate skeletons make up their primary structure • An extraordinary diversity of organisms flourishes in these spectacular habitats Coral Reefs • Coral animals are tiny relatives of jellyfish that live together in vast numbers • Most coral animals are the size of your fingernail, or even smaller • Each one looks like a small sack with a mouth surrounded by tentacles • These animals use their tentacles to capture and eat microscopic creatures that float by • Coral animals cannot grow in cold water or water that is low in salt Coral Reefs • The types of corals that build reefs grow with the help of algae that live symbiotically within their tissues • These algae carry out photosynthesis using the coral animals' wastes as nutrients • In turn, the algae provide their coral hosts with certain essential carbon compounds • Because their algae require strong sunlight, most reef-building corals thrive only in brightly lit areas within 40 meters of the surface Open Ocean • The open ocean, often referred to as the oceanic zone, begins at the edge of the continental shelf and extends outward • It is the largest marine zone, covering more than 90 percent of the surface area of the world's oceans • The open ocean ranges from about 500 meters deep along continental slopes to more than 11,000 meters at the deepest ocean trench • Organisms in the deep ocean are exposed to high pressure, frigid temperatures, and total darkness Open Ocean • Typically, the open ocean has very low levels of nutrients and supports only the smallest producers • Productivity is generally low • Still, because of the enormous area, most of the photosynthetic activity on Earth occurs in the part of the open ocean within the photic zone • Fishes of all shapes and sizes dominate the open ocean • Swordfishes and octopi are just two examples of the organisms found in this zone • Marine mammals such as dolphins and whales also live there but must stay close to the surface to breathe Benthic Zone • The ocean floor contains organisms that live attached to or near the bottom, such as sea stars, anemones, and marine worms • Scientists refer to these organisms as the benthos • That is why the ocean floor is called the benthic zone • This zone extends horizontally along the ocean floor from the coastal ocean through the open ocean Benthic Zone • Benthic ecosystems often depend on food from organisms that grow in the photic zone, particularly the producers • Animals that are attached to the bottom or do not move around much, such as clams and sea cucumbers, feed on pieces of dead organic material, or detritus, that drift down from the surface waters • Near deep-sea vents, where superheated water boils out of cracks on the ocean floor, dwell chemosynthetic primary producers that support life without light and photosynthesis